Abrasive articles and method of making the same



I nnmsivniancms-m ETHOD oF 1 MAKINGTHESAMEV,

George Pr'Nethei-l y and Bert SQCross, St. Paul, Minn.,' and Gilbert R. Anderson, Wilmingto Tnennssignm to Minnesota Mining a Mann- 1 facturing Compa y;

tion of Delaware Paul,

Minn, a corporat r NofDrawing. Application March 20;1941, q a s rininasssn o;

5'Claimsr "(c1.ts1-'-2' oc)fj f a v I .producingmaximuin shearing eifectof the work- This invention relates; in general, to articles or i v I 1ing article. ,By orientation of an abrasivegran manufacture of the type having a. support and" a* layer' of comminuted solid. materials deposited and secured thereon; and more particularly improvements'in securing and'maintaining a, physical'union of the comminuted material to' itsf support. v v

The invention is particularly directed. to; the? coating of supports such'as' strips'or sheets of fabric, paper, or the like,- with abrasiveparticles -ule, we-niean-a disposition of the granular mate-1 or granules and theapplication of their securing 2v means for adherence articles. I

- This application is a' continuation-in-part of our-copending application. Serial No." 179,338,- flied thereto to' 'make abrasive rial coated on a bonding surface in, such a manner that'the longer dimensional configuration of the granular material is placedapproximately perpendicular'tothe bond;Present methods of apiply'ing 'orientedparti cles arejamply illustrated by a I I relectrostaticmeans as described in the patent to 3. Sl-jSimfyser;No.11,788,600.' l

{5 1 Ourf'invention'is' notv concerned with the problems of applying the abrasive particles in a par- 1; ticular manner to 'thebasematerial; but'is con-v 'cerned primarily with the provision. of. a coi'nbias sandpaper or'emery cloth .compr-ise'generally.

(a). a base of sheetmateriaL-which maybe felted I as in the case of paper or woven as in the case" of cloth (b) a more or less finely comminuted re'-'- sistant material having abrading properties, such The manufactured'abrasive articles known to as'garnet, corundum', or the likegand (c) a binder generally in the form of a glue orresinous bond I which s'ervesto' bind the abrasive to the base.

nation gof individually distinct and separate jadj 1 I hesive' coatings coi-operatively" maintaining" the a j particles in the original position obtained' in their first application to the base. This position is pref erablysuch'that the particles are oriented so that alsiubstantial proportion r their pointed abrasive-surfaces areexposcd, or'at least such that particles are disposed with the long dimensions thereof at a substantial angle to the base.

It is therefore a principal object of this invention to secure a maintenanceof orientation of abrasive vparticlesadhering to a primary or makus haveat no time in the past everjbeen made so that all abrasive particles are'coated and held in a durable matrix or solidified adhesives insuch a manner that substantially an of the particles have an opportunity of rendering" full utility.

The abrasive particles, to be firmlysecured', require an additional bond or a plurality of bonds to anchor them to the adhesive on which theyare coated. This additional bonding givesthefin ished abrasive article additional strength and Generally this destruction or changing of posiapplication ing adhesive coated on a base, duringand after ing.

Another v an abrasive article having a better cutting edge due to coating of the-particles in such a manner orientation of the abrasive particles on. abrasive articles, both "as to those having a substantially rigid backing and those having a flexible backtion of the particles maybe described as due to' 3 the disturbing forces of a later applied bonding means; tending to pull the granule. loosened by .a

softening ofthe original binder,. from its original position.

With the present type of application of oriented granularparticles to anadhesive-bond, a particular need is present of maintaining the gran-' v ingyand the invention is applicable to preparing abrasive articles both for dry abrasive work and wet abrasive work. t r

In addition, we have further found thatlthe application of the bonding materials in accordance with our invention results in an abrasive. article fh aving increased life'and durability as well'asa'strengthenedgranular bond.

a ordanc flwith'the present invention; the ry'or making coat of adhesive (upon which a the coinniinutedsolid materialis deposited as a ules in an oriented posltlonfor the'purpose oil-e0 layerorcoating and the second anchoring or of a second anchoring adhesive'coat object of this I invention to provide be i-othe'rwise treated-as heretofore mentioned.

3. Simllarresults are obtained where a resin,

tion of the anchoring binder coating from'looseningthe: bond between theprimary adhesive and the comminuted material.- l-loweven afterappli-z cation of some of the type adhesives as hereinafter expressed, aslight softening effect; may be i produced by heat treatments or the like, tending to-fuse the? bonds. Such slight softening-effect does not destroy the oriented -position of 1 the granule, but tends to provide a more stable bond f between dual binding means.

The nature of the invention will be apparent in more detail from the following examples an descriptions by which it is illustrated:

v1. A glue-resin This adhesive composition is coated on a adhesive is'made up consist" g l 1 Having accomplished a partial polymerization of v .passedinto the formaldehyde chamber or be for example a'phe'nol-aldehyde or heat-advanclug resin soluble in the alcohols as methyl and the like orfketones .as 1 acetone or organic esters as ethyl -acetate',;etc., is used as aprimary watch a backing." The mineralis coated directly on the v.adhesi 're '.phenolaldehydesurface. 1 Sufllcie'nt 'heat is then directed on themineral coated'back- :fingto volatilize the solvent and polymerize the resin. The'temperatur'e employed generally will .run from 150 F. to 225F. or higher as applicable tothe-materialsused. v'Ihe'time varies from minutes to several ';hours" depending upon the amount of resin coated and the temperature used.

the resin, we are then able to add additional resin in the form of anchoring adhesive without affecting orientation because the resin onc'e properly set .up will not be further. affected by the solvents in the anchoring coat, with a like treat- 1 .Parts Glue Phenol-aldehyde resin v82v Water j 66 Urea 13 Concentrated ammonia 1 241 Cellosolv'e (ethylene glycol monoethyl" I ether) 1 material such as cloth, paper, or the like, as the a primary or making coat. Abrasive granules are then oriented or coated onthis adhesivea'ndileft to dry at room temperature for approximately 20 minutes. The sheet so dried is then coated with a phenol-aldehyde resin solution which co sists of:

again dried. as above. The solvent Cellosolve used inthis second anchoring adhesive has no efiect on the primary bond to the extent of caus-.

facial surfaces of this typ bond without a destruction of the granular positioning.

4; Anotherexample'of the type bonding materials which we propose using is a primary adhesive coating applied asa base or binder for disposition of abrasive granular 'mineral, for ex-- ample glue and resin soluble, e. g. in alcohol and water, which can be, by heat treatment as is commonly known to the trade, hardened sumciently tohold the granules in place, and then a coating 'of. a resin such as Bakelite, or other phenol-alde- Jhydes or heat-advancing resins, or styrene, vinyl- .ite resins and the like, which contains no solvent and is normally liquid at room temperature, is applied over the granules and the coated article isthen subjected to .a temperature which will [polymerize or set up the resin beginning at aping the abrasive mineral to lose its oriented position, the primary bond having been insolubilized to any mono-constituent'solvent by evaporation of the solvents water and Cellosolve. 2. Another example of the use of this principle of coating is .toinsolubilize a coating'o'f adhesive through direct chemical reactions, such as by a tanning reaction, or by heating. In this case, for example, a coating of glue of the usual type is applied to the abrasive backing and then the abrasive material is coated to the adhesive.) The glue-coated backing with abrasive thereon is then passed into 9. formaldehyde gas-fllled-chamber wherein the glue is converted from afilmsoluble proximately 110 Faand notexceeding the limit at which'carbonization takes place.

5. Other-methods of accomplishing a maintenance of-orientation include use of a hydrophylic primary casein binder adhesive and an'anchoring in water to one insoluble in water.) A second coating of glue is then applied as an anchoring formaldehyde, furfural; acetaldehyde, or the-like;

picricacid or itssalts',"chrome. alum, sodiumdi'-' chromate, dichromic acid oriits salts, titanium oxide, stannous .chloride," hexamethylenetetramine, or the Ilka-any and all of which will render the adhesive substantially water-insoluble and weather-resistant. The anchoring'bondsubsequently added has no effect on the original position of the mineral particles because'the 'solventof the second coating does not-afiectthe primary securing means. ,To render theanch'oring bond water-insoluble, the article may again .means for securing the abrasive material. over the original glue film- In place ofthe specific formmethacl'ylalte P ymer solution in benzene used as aldehyde 2 5 there maybe substituted par v I adhesive of a phenol-aldehyde resin in organic solvents which do not dissolvethe caseinbinder; a'sodium silicate primarybinderadhesive soluble in water-and a resin anchoring-size as chloroprene, vinyl derivative, or" the like applied in a liquid state and polymerized, for example, by heat and pressure, light, or a catalyst such as o y en or a peroxide. -An additional illustration is the application of a phenol-aldehyde resin soluble in ethylene glycol monoethyl ether which serves as a good primary coating and maintains orientation well when employed in conjunction with N-propyl an anchoring adhesive.

' Inaddition-to the above enumerated examples,

- mayibemade of an anchoring adhesive (such asta resin) fin-an organic solvent, which may be any ketonegpolyethu, ester, ethyl alcohol, methyl alcohol, ffurfurane derivative, any chlorinated solvent or any other organic solvent or mixture of organic solvents, in conjunction with a primary binder adhesive or bond dissolved in water, but

not soluble in the particular solvent used in the anchoring. adhesive. Conversely, we may make use of an anchoring adhesive'dissolved in water I and a water-insoluble primary binding bond dis- 3 solved in an organic solvent as of the above character.

u e; of a blood albumin anchoring adhesive in These possibilitie are illustrated by the water and a primary resin binder adhesive soluble in a hydrocarbon of the above character; by a primary casein glue binder adhesive in water and a resin anchoring adhesive in an organic solvent, such as ether alcohols, esters. and the like, in which the glue is insoluble; and by water-soluble soybean protein glue as the primary binder adhesive and a resin anchoring means in an organic solvent, such as benzene, ether, alcohol and the like, in which the soy protein is insoluble; any and all of which coatings may be used in vice versa or interchangeable form as contemplated by this improved combination of bonding means.

Further, by way of illustration, we may use an anchoring adhesive dissolved in an organic solvent. and a primary binder bond dissolved in another organic solvent, but not soluble in the particular solvent used in the anchoring adhesive. As an example of this type of bonding means, in addition to those already given, we may use a primary binder coating of a proteide type. such as zein or the like, in alcohol, and a resin anchoring coating having an organic solvent in which the primary binder is insoluble such as benzene, ether, chlorinated methane, and the like.

As an alternative method of applying coatings dissolved in the same solvent, we have found that we may apply the granules to a primary adhesive coating and then by the use of a thin interposed covering of material such as a sulphonated rubber (for example an acid seal primer which is a-commercial preparation of sulphonated rubber made by Goodrich), with or without a modifier, applying a sizing coat dissolved in the same solvent as the binder coat to secure a finished product with the granules in an oriented position. With the addition of this thin coating and sealing material, we have in reality applied three films for securing the abrasive granules and find that it is possible, by the use of the intermediate sealing layer (such as that previously mentioned or any equivalent layer which will meet the requirements of preventing the anchoring coating from attacking the primary or making coat and of securing a good intermediate cohesion between the making and the sizing bonds), to interchangeably use the bonding means in any form or combination desired, whether dissolved in a like solvent or not.

By the methods as herein disclosed, the primary binder and anchoring coats are co-operatively distinct in the product, although adhering or bonded together at the interface without destroying the granular position.

In general, it is our desire to use the examples illustrated in any combination which will accomplish the purpose of our invention, or any substitutes thereof which by nature have characteristics for accomplishing the results herein described; and while we have described more or less specifically the application of certain coatings, it will be readily understood that other combinations of adhesives may be applied for the purpose of securing maintenance of orientation.

Furthermore this application is not limited to the combination of adhesive coatings specifically illustrated above, and contemplates broadly the use of particular advantageous resinous and adhesive materials as a bond or binder for abrasive grits. For example, acrylic resins have been found by us to have special advantages in bonding abrasive grits. In addition to the polymerized acrylic ester given herein above, we may use as a bond for abrasive grits (or as a presize or the like in the case of coated abrasives) other acrylic resins, of which polymers of N-butyl methacrylate, iso-butyl methacrylate, ethyl methacrylate and methyl methacrylate, and copolymers made from such compounds are important examples. 'Ihe copolymers may be of any two or more monomers of the materials named, or between a monomer or partial polymer of any one of the acrylic materials 'hereinabove set out and another acrylic monomer or partial polymer and/or a vinyl monomer, or other comparable polymerizable materials, for controlling hardness and/or other properties, as desired. The control of hardness of acrylic acid resins (such as methacrylate ester polymers, etc.) by copolymerization has, in a general way, long been well known in the resin art. For example, see generally The Chemistry of Synthetic Resins" by Ellis (1935), page 1076 etc.; British Patent No, 374,436 of 1931; Chemical Abstracts, 1934, vol. 28, page 4379; Synthetic Resins and Their Plastics by Ellis (1923), page 304 and footnotes; etc. Hardness can also be controlled by the use of plasticizers,

especially those known in the resin art with which the acrylic resin is compatible but may or maynot be actually soluble. Where a plasticizer is used in which the acrylic resin is not actually soluble, in addition to avoiding undue hardness of the bond, this aids in producing an abrasive article which tends to maintain or return to its original shape or form. The proper c der of hardness in any case is well known to those familiar with the manufacture of abrasive articles, e. g. sandpaper.

We also advantageously control hardness, flexibility or other properties of methacrylates, ethacrylates or other acrylic resins by blending or homogenizing the same, in any suitable manner well known to resin chemists, with other resinous materials including vinyl chloride-acetate copolymers, chlorinated rubber, e. g. Tornesite," and/or cellulose nitrate, or with rosin, certain phenol aldehyde resins, coumaroneindene resins and/or chlorinated diphenyl, for example, choosing the blending agent or resin and proportion thereof in any case so as to secure desired uniformity. Also acrylic resins may be flexibilized for use in abrasive articles such as sandpaper by the use of such plasticizers as dibutyl phthalate, dicyclohexyl phthalate, dibutoxyethyl phthalate, dibutoxyethyoxyethyl phthalate, triethylene glycol dihexoate, and the six to twelve carbon branch chain secondary alcohol carbamates. Materials such as methyl abietate may also be used with many acrylic resins.

The acrylic resins may be employed with or without solvents but solvents are often desirable. Suitable solvents include Cellosolve, aromatic hydrocarbon esters, ketones, ethers, and chlorinated hydrocarbons.

While we have described and illustrated our invention in various details, we do not limit ourselves thereby. All novel subject matter disclosed and/or embraced within the scope of the appended claims is comprehended as our invention.

What we claim is:

1. As a new article of manufacture, abrasive grains bonded with a polymerized ester of alkyl substituted acrylic acid.

2. As a new article of manufacture, an abrasive article of the coated abrasive type comprising abrasive grains bonded with a polymerized mono-hydric alcohol ester of alkyl substituted acrylic acid.

3. As a new article of manufacture, a coated abrasive article comprising abrasive grains bonded with a copolymer of a vinyl ester and a polynierizable ester of an alkyl substituted acrylic acid.

4. As a new article of manufacture, sandpaper having abrasive grains bonded with an adhesive composition including N-propyl methacrylate.

5. As a new manufacture, an abrasive article 5 tuted acrylic acid.

including a sandpaper backing and comprising abrasive grains bonded and anchored thereto with an adhesive composition including a polymerized ester of an alcohol and an alkyl substi- GEORGE P. NETHERLY. BERT S. CROSS. GILBERT R. ANDERSON.

DISCLAIMER 2,357,348.Ge0rge P. Netherl'y and Bert 8. Gross, St. Paul, Minn., and Gilbert R.

nderson, Wilmington, Del. ABRASIVE ARTICLES AND METHOD OF Meme THE SAME. Patent; dated Sept. 5, 1944. Disclaimer filed July 18, 1947, by the assignee, Minnesota Mining (ff Manujactufing Company. Hereby enters this disclaimer to Claims 1', 2, 3, and 5 of said patent. [Oflicial Gazette August 26, 1947.] d 

